Example embodiments generally relate to the field of photonics integrated circuits (PICs) lateral couplers. For example, an example embodiment provides a gradient-index (GRIN) waveguide lateral coupler.
Technologies for producing compact optical communication systems are available using complementary metal-oxide-semiconductor (CMOS) compatible processes, for example, in the form of PICs. Efficient coupling between a PIC waveguide and an external optical fiber, however, can be a major challenge due to a modal mismatch at the waveguide-optical fiber interface. The modal mismatch of coupling between PIC waveguides and external optical fibers can be a larger challenge when the optical fiber is outside the plane of the waveguide (e.g., when the waveguide-optical fiber interface is not perpendicular to the direction of propagation defined by the waveguide), due to the guided nature of the waveguide modes. Currently, grating couplings are generally used to couple out-of-plane optical fibers to PIC waveguides. For example, grating couplings are generally used as waveguide lateral couplers. Grating couplings however, can be difficult to design and manufacture and generally result in a significant loss of beam power.
Therefore, a need exists in the art for improved methods, devices, and/or the like for coupling PIC waveguides to external optical fibers.